The present invention relates to a rotating disk type storage unit, and is suited to a rotating disk type storage unit, in which a voice coil motor drives an actuator mounting thereon a head.
A magnetic disk apparatus exemplary of a rotating disk type storage unit drives an actuator mounting thereon a magnetic head to thereby position the magnetic head that performs recording or reproduction of information on a magnetic disk. Used as a drive source for the actuator is a voice coil motor comprising a voice coil mounted on one end of the actuator, a magnet arranged in opposition to the voice coil, and a voice yoke member that forms a magnetic circuit. A thrust moment of the actuator is obtained from electric current applied to the voice coil of the voice coil motor and a magnetic circuit formed by the magnet and the voice yoke member.
In conventional magnetic disk apparatuses, there is disclosed a construction in JP-B-61-46901 (Patent Document 1), in which a thrust moment generated in a voice coil is made uniform in a range of movement of the voice coil.
With such magnetic disk apparatus, a length in a direction perpendicular to a direction of movement of the voice coil is made long from a central portion thereof to an edge thereof by forming a magnet such that its length perpendicular to the direction of movement of the voice coil is made long from a central portion thereof to an edge thereof. In such construction, a thrust moment tending to become small at ends of the range of movement of the voice coil is made uniform in the range of movement of the voice coil.